This invention deals with removal of the washing solvent from an offset blanket after it has been washed with solvent to remove the ink image and, more particularly, with a device capable of collecting and conducting away either through capillary action or capillary action and the force of gravity, the small quantity of liquid left behind as a result of the washing operation.
The process of lithographic duplicating usually involves the use of a resilient rubber blanket to which is transferred the ink image created on the master and which is ultimately transferred to impression paper. Such a blanket is generally referred to in this art as an offset blanket.
In the typical construction of a lithograhic duplicator, the printing instrumentalities are mounted on a series of cylinders which give rise to a master cylinder on which is carried the lithographic master, a blanket cylinder on which is carried the resilient offset blanket, the impression cylinder which merely serves to help transfer the ink image from the blanket to the impression paper.
At the end of a duplicating cycle, it is necessary to remove the residual ink image by cleaning the blanket, in preparation for the next duplicating cycle.
The number of techniques and devices which are disclosed and described in the prior art are numerous in terms of applying a suitable solvent for washing away the ink thereby cleaning the blanket. A wide variety of techniques for cleaning the blanket are known, including the use of sponges and applicators which turn both concurrent and countercurrent to the blanket cylinder; some of which include power driven scrubbers and the like. All are calculated to effectively apply the solvent to the ink layer to wash it away from the surface. Inevitably, there remains on the blanket surface, a thin layer of solvent which must be removed and the blanket surface appropriately dried in advance of the next duplicating cycle. If the blanket is not appropriately dried, copies of inferior lithographic quality will result.
The chemical composition of such solvents has been formulated to satisfy a number of requirements imposed by the duplicating system. They must, of course, have appropriate solvency for the ink but at the same time have sufficiently high flash points to avoid a fire hazard. Toxicity is an important factor. Materials having the appropriate degree of solvency for the ink but a high toxic hazard cannot be used. Methods which depend on evaporation cannot deal effectively with the conflicting requirements of rapid removal and low air contamination level. Since this apparatus accumulates and removes the excess wash solvent quickly and in liquid form, the problem of toxicity is virtually eliminated and the selection of a suitable solvent far simpler.
It is desirable in the operation of a lithograhic duplicating machine to complete each of the operations as quickly as possible in order to proceed with the productive printing operations. This is especially true of a highly automated lithographic duplicator which may be used for printing only five or six copies of each master. Under these circumstances, cleaning and drying the blanket takes nearly as long as printing the copies.
It is a general object of the present invention to provide an improved device for rapidly removing solvent from the offset blanket remaining from the ink washing operation quickly and effectively in a very short period of time.
It is a further object of the present invention to provide a device for quickly and effectively removing all necessary solvent remaining on the blanket without the use of special devices that cause the material to evaporate into the working environment or the use of suction devices that operate with large volumes of air being passed through the system.
It is a still further object of the present invention to provide a highly effective and simply constructed, easy to operate device for removing sufficient solvent remaining from the ink washing operation of the blanket by means of a wiper which collects the solvent liquid and directs the liquid into a capillary channel for removal to a waste collecting reservoir.
It is a specific object of this invention to provide a highly effective solvent removal device that collects the fluid and conducts it away without the need for using large volumes of air induced by high vacuum, heat or other procedures that cause the evaporation of the solvent into the atmosphere and can dry the blanket in one or two revolutions of the blanket cylinder.